The characteristics and features of AMPS-D and IS-54 are described in the parent application. Cellular telephone systems such as are described in the co-pending application as well as other cellular telephone systems are designed to efficiently connect the mobile subscriber to a conventional telephone connected in the Public Switched Telephone Network (PSTN). There are other applications however in which the architecture is either inefficient or incapable of performing a desired function.
One area in which this architecture is inefficient relates to the transmission and the reception of data via standard protocols such as X.25, NSA, TC/IP etc.
Another problem area is dispatch or fleet call operations. A dispatch or fleet call, contrary to a typical cellular telephone call, is a point-to-multipoint operation. A typical dispatch or fleet call voice message is relatively short and it is inefficient to require a dispatch operator to identify each of the perhaps many individuals to whom the message is to be sent, each time a message was transmitted. In addition, the hierarchy described in the co-pending application does not lend itself to efficient mobile-to-mobile conversations even on a point-to-point basis. More particularly, as described in the co-pending application the PSTN is interfaced to a Mobile Switching Center (MSC). The MSC is connected to a base station sub-system which includes at least one Base Station Controller (BSC) and one or more Base Transceiver Stations (BTS). One of the functions of the BSC is that of expanding compressed speech passing from the mobile to the PSTN in one direction and compressing voice traffic passing from the PSTN to the mobile. As a result, in a mobile-mobile call, under certain conditions compressed speech from the mobile is first expanded in a BSC, passed on to the MSC where it is switched back to a (different) BSC. At that point, the expanded speech is then compressed for transmission to the receiving mobile. This double coding of speech is unduly expensive in that it unnecessarily uses coding capacity. Furthermore, the double coding is deleterious to the maintenance of quality in voice traffic.